.....They don't tell you what the assignment is or the pay until you accept. ...
You may be over looking it. If you go into the project (online) click on the GENERAL tab and then scroll down on the left (it's a long contract) the rate /Compensation is listed on the last page, or at least that's how mine have been.
Mine average a good deal more per job than you've stated but I'd imagine it depends on what their client is willing to pay. Not including drive time (I'll already be in the area) I'm estimating I'll be making about $125/hr on my next project with them.